package com.example.mq.mqserver;

import com.example.mq.common.*;
import com.example.mq.mqserver.core.BasicProperties;

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * @Description: 消息队列本体服务器
 * @Author: liudong
 * @Time: 2024/5/21
 */

public class BrokerServer {
    private ServerSocket serverSocket = null;
    //目前一个brokerserver上只有一个虚拟主机
    private VirtualHost virtualHost = new VirtualHost("defult");
    //使用这个hash表，表示当前会话，也就是哪些客户端和服务器正在连接
    //此处的key是channelId
    private ConcurrentHashMap<String, Socket> sessions = new ConcurrentHashMap<String, Socket>();
    //引入线程池操作
    private ExecutorService executorService = null;
    //引入boolean变量控制服务器是否继续运行
    private volatile boolean runnable = true;

    public BrokerServer(int port) throws IOException {
        serverSocket = new ServerSocket(port);
    }

    public void start() throws IOException {
        System.out.println("[BrokerServer] 启动！");
        executorService = Executors.newCachedThreadPool();
        while (runnable) {
            Socket clientSocket = serverSocket.accept();
            //把处理连接的逻辑丢给这个线程池
            executorService.submit(() -> {
                processConnection(clientSocket);
            });
        }
    }

    //一般来说，停止服务器就是直接kill掉对应进程
    public void stop() throws IOException {
        runnable = false;
        //把线程池中的线程都放弃了，让线程都销毁
        executorService.shutdown();
        serverSocket.close();
    }

    /**
     *
     * @param clientSocket
     */
    //通过这个方法，处理一个客户端的连接
    //在这一个连接中，可能会涉及到多个请求和响应
    private void processConnection(Socket clientSocket) {
        try (InputStream inputStream = clientSocket.getInputStream();
             OutputStream outputStream = clientSocket.getOutputStream()) {
            //这里需要按照特定格式来读取并解析，此时就需要用到DataInpuStream
            try (DataInputStream dataInputStream = new DataInputStream(inputStream);
                 DataOutputStream dataOutputStream = new DataOutputStream(outputStream)) {
                while (true) {
                    // 1. 读取请求并解析.
                    Request request = readRequest(dataInputStream);
                    // 2. 根据请求计算响应
                    Response response = process(request, clientSocket);
                    // 3. 把响应写回给客户端
                    writeResponse(dataOutputStream, response);
                }
            }
        } catch (EOFException | SocketException e) {
            // 对于这个代码, DataInputStream 如果读到 EOF , 就会抛出一个 EOFException 异常.
            // 需要借助这个异常来结束循环
            System.out.println("[BrokerServer] connection 关闭! 客户端的地址: " + clientSocket.getInetAddress().toString()
                    + ":" + clientSocket.getPort());
        } catch (IOException | ClassNotFoundException | MqException e) {
            System.out.println("[BrokerServer] connection 出现异常!");
            e.printStackTrace();
        }  finally {
            try {
                //当连接处理完了就需要关闭socket
                clientSocket.close();
                //一个tcp连接可能包含多个channel，需要把当前这个socket对应的channel也顺便清理掉
                clearCloseSession(clientSocket);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }


    private Request readRequest(DataInputStream dataInputStream) throws IOException {
        Request request = new Request();
        request.setType(dataInputStream.readInt());
        request.setLength(dataInputStream.readInt());
        byte[] payload = new byte[request.getLength()];
        int n = dataInputStream.read(payload);
        if (n != request.getLength()) {
            throw new IOException("读取请求格式出错！");
        }
        request.setPayload(payload);
        return request;
    }

    private void writeResponse(DataOutputStream dataOutputStream, Response response) throws IOException {
        dataOutputStream.writeInt(response.getType());
        dataOutputStream.writeInt(response.getLength());
        dataOutputStream.write(response.getPayload());
        //刷新缓冲区，可以让其快速进入网卡，不至于在内存里呆着
        dataOutputStream.flush();
    }

    /**
     *
     * @param request
     * @param clientSocket
     * @return
     * @throws IOException
     * @throws ClassNotFoundException
     * @throws MqException
     */
    private Response process(Request request, Socket clientSocket) throws IOException, ClassNotFoundException, MqException {
        //1.把request中的payload做一个初步的解析
        BasicArguments basicArguments = (BasicArguments) BinaryTool.FromBytes(request.getPayload());
        System.out.println("[Request] rid=" + basicArguments.getRid() + "channelId =" + basicArguments.getChannelId()
                + "type=" + request.getType() + "length=" + request.getLength());
        //2.根据type的值，来进一步区分接下来这次请求要干啥
        boolean ok = true;
        if (request.getType() == 0x1) {
            //创建channel
            sessions.put(basicArguments.getChannelId(), clientSocket);
            System.out.println("[BrokerServer] 创建channel完成！channelId=" + basicArguments.getChannelId());
        } else if (request.getType() == 0x2) {
            //销毁channel
            sessions.remove(basicArguments.getChannelId());
            System.out.println("[BrokerServer] 销毁channel完成！channelId=" + basicArguments.getChannelId());
        } else if (request.getType() == 0x3) {
            //创建交换机，此时payload就是ExchangeDeclearArguments对象了
            ExchangeDeclareArguments arguments = (ExchangeDeclareArguments) basicArguments;
            ok = virtualHost.exchangeDeclare(arguments.getExchangeName(), arguments.getExchanegType(),
                    arguments.isDurable(), arguments.isAutoDelete(), arguments.getArguments());
        } else if (request.getType() == 0x4) {
            ExchangeDeclareArguments arguments = (ExchangeDeclareArguments) basicArguments;
            ok = virtualHost.exchangeDelete(arguments.getExchangeName());
        } else if (request.getType() == 0x5) {
            QueueDeclareArguments arguments = (QueueDeclareArguments) basicArguments;
            ok = virtualHost.queueDeclare(arguments.getQueueName(), arguments.isDurable(),
                    arguments.isExclusive(), arguments.isAutoDelete(), arguments.getArguments());
        } else if (request.getType() == 0x6) {
            QueueDeleteArguments arguments = (QueueDeleteArguments) basicArguments;
            ok = virtualHost.queueDelete(arguments.getQueueName());
        } else if (request.getType() == 0x7) {
            QueueBindArguments arguments = (QueueBindArguments) basicArguments;
            ok = virtualHost.queueBind(arguments.getQueueName(), arguments.getExchangeName(), arguments.getBindingKey());
        } else if (request.getType() == 0x8) {
            QueueUnbindArguments arguments = (QueueUnbindArguments) basicArguments;
            ok = virtualHost.queueUnbind(arguments.getQueueName(), arguments.getExchangeName());
        } else if (request.getType() == 0x9) {
            BasicPublishArguments arguments = (BasicPublishArguments) basicArguments;
            ok = virtualHost.basicPublish(arguments.getExchangeName(), arguments.getRoutingKey(), arguments.getBasicProperties(), arguments.getBody());
        } else if (request.getType() == 0xa) {
            BasicConsumeArguments arguments = (BasicConsumeArguments) basicArguments;
            ok = virtualHost.basicConsume(arguments.getConsumerTag(), arguments.getQueueName(), arguments.isAutoAck(),
                    new Consumer() {
                        //这个回调函数要做的就是 把服务器收到的消息可以直接推送回对应的消费者客户端
                        @Override
                        public void handleDelivery(String consumerTag, BasicProperties basicProperties, byte[] body) throws MqException, IOException {
                            //先知道当前这个收到的消息，要发给哪个客户端
                            //此处 consumerTag 其实是channelId ，根据channelId去session中查询，
                            //就可以得到对应的socket对象了，从而可以往里面发送数据了
                            //1.根据channelId找到socket对象
                            Socket clientSocket = sessions.get(consumerTag);
                            if (clientSocket == null || clientSocket.isClosed()) {
                                throw new MqException("[BrokerServer] 订阅消息的客户端已经关闭了！");
                            }
                            //2.构造响应数据
                            SubScribeReturns subScribeReturns = new SubScribeReturns();
                            subScribeReturns.setChannelId(consumerTag);
                            subScribeReturns.setRid("");
                            subScribeReturns.setOk(true);
                            subScribeReturns.setConsumerTag(consumerTag);
                            subScribeReturns.setBasicProperties(basicProperties);
                            subScribeReturns.setBody(body);
                            Response response = new Response();
                            byte[] payload = BinaryTool.toBytes(subScribeReturns);
                            //0xc 表示服务器给消费者客户端推送的消息数据
                            response.setType(0xc);
                            //response的payload就是一个SubScribeReturns
                            response.setLength(payload.length);
                            response.setPayload(payload);
                            //3.把数据写回给客户端
                            //此处的dataOutputStream这个对象不能close！！！
                            //这个关了之后mclientSocket中的outputStream也会关闭
                            //此时就无法继续往socket中写入后续数据了
                            DataOutputStream dataOutputStream = new DataOutputStream(clientSocket.getOutputStream());
                            writeResponse(dataOutputStream, response);
                        }
                    });
        } else if (request.getType() == 0xb) {
            //调用basicAck来确认消息
            BasicAckArguments arguments = (BasicAckArguments) basicArguments;
            ok = virtualHost.basicAck(arguments.getQueueName()
                    , arguments.getMessageId());
        } else {
            //当前的type是非法的
            throw new MqException("[BrokerServer] 未知的type！ type = " + request.getType());
        }
        //3.构造响应
        BasicReturns basicReturns = new BasicReturns();
        basicReturns.setChannelId(basicArguments.getChannelId());
        basicReturns.setRid(basicArguments.getRid());
        basicReturns.setOk(ok);
        byte[] payload = BinaryTool.toBytes(basicReturns);
        Response response = new Response();
        response.setType(request.getType());
        response.setLength(payload.length);
        response.setPayload(payload);
        System.out.println("[Respose] rid =" + basicReturns.getRid() + "channelId = " +
                basicReturns.getChannelId() + "type=" + response.getType() + "length = " + response.getLength());
        return response;
    }

    /**
     * 清除过期的会话
     * @param clientSocket
     */
    private void clearCloseSession(Socket clientSocket) {
        //这里主要做遍历上述session hash表，把该被关闭的socket对应的键值对，统统删掉
        List<String> toDeleteChannelId = new ArrayList<>();
        for (Map.Entry<String,Socket> entry :sessions.entrySet()){
            if (entry.getValue() == clientSocket){
                //对于同一个变量，不能一边遍历一边删除
                toDeleteChannelId.add(entry.getKey());
            }
        }
        for (String channelId : toDeleteChannelId){
            sessions.remove(channelId);
        }
        System.out.println("[BrokerServer] 清理session完成！被清理的channelId = "+toDeleteChannelId);
    }


}
